Xurukk, Warden of Madness

Boon of Combat Prowess: Once per long rest, when you miss with a melee weapon attack, you can choose to hit instead

Relentless Endurance: Once per long rest, when you drop to 0 hitpoints, drop to 1 instead.

Savage Attacker: When you score a critical hit, you may roll the weapon dice one additional time.

Karsus' Boon of Greater Magic: Your charisma score increases by 6 to a maximum of 26.

Scythe of Karsus: +3 Weapon. Due to the pact of the blade, this can also be used as your spellcasting modifier. Any psychic damage you do while holding this weapon, heal by half of the damage total, up to a maximum of 50 health per turn. This health can not increase beyond your maximum

Otherworldly Patron: Your patron is Karsus, Son of Madness. He is the God of Madness.

Eldritch Invocations:

Agonizing Blast: Add your charisma modifier (+8) as extra damage to your Eldritch Blast

Repelling Blast: Whenever you hit with your Eldritch Blast, you can push the target up to 10 feet away.

Eldritch Spear: The range of your Eldritch Blast is 300 feet.

Thirsting Blade: You may attack twice with your pact weapon when you use the attack action

Lifedrinker: Your pact weapon deals extra damage equal to your charisma modifier (+8) This damage is already factored in.

Eldritch Mind: You have advantage on concentration saving throws

Sculptor of Flesh: Once per long rest, you can cast polymorph using a 4th level warlock spell slot.

Relentless Hex: Once per turn, you may teleport 5 feet away from your target as long as you are within 100 feet, and they are affected by your Hexblades Curse.

Maddening Hex: If a creature is affected by your Hexblades curse, they automatically take psychic damage equal to your charisma modifier at the start of their turn.

Trickster's Escape: Once per long rest, you may cast Freedom of Movement without spending a spell slot.

Pact of The Blade: Your weapon is considered magical and you cannot be disarmed.

Eldritch Master: Once per long rest, you may rest for one minute to regain all of your spell slots.

War Caster: +2 on concentration saving throws, ability to cast spells with somatic components with no hands free, when a creature provokes an opportunity attack, you may cast a spell instead.

Spellcasting. Xurukk is a 25th level spellcaster. Their spellcasting ability is Charisma (spell save DC 27, +19 to hit with spell attacks). Xurukk has following Warlock spells prepared:
Cantrips (at will): Eldritch Blast, Green Flame Blade, Sword Burst, Infestation

5th level (6 slots): Enervation, Far Step, Negative Energy Flood, Synaptic Static, Staggering Smite, Phantasmal Killer, Blight, Elemental Bane, Shadow of Moil, Spirit of Death, Spirit Shroud, Hunger of Hadar, Vampiric Touch, Mind Spike, Crown of Madness, Branding Smite, Arms of Hadar, Armor of Agathys, Hellish Rebuke, Cause Fear, Wrathful Smite

6th level (1 slot): Eyebite

7th level (1 slot): Finger of Death

8th level (1 slot): Maddening Darkness

9th level (1 slot): Psychic Scream

Scythe of Karsus. Melee Weapon Attack: +19 to hit, reach 10 ft cone. Hit: 38 (1d12 + 20) slashing damage and 2d10 Psychic damage.

When you hit an enemy the Scythe of Karsus, their madness point total increases by 10% (minimum of 10 points)

Inflict Madness (1/day): Pick a target creature within 100 feet of you. You speak a vile incantation causing them to make a madness wisdom save. On a failure, immediately gain 200 points on the madness table, on a success, gain half as much.

Hexblades Curse: As a bonus action, you can inflict your Hexblades Curse on a creature. The creature takes extra damage equal to your proficiency bonus (+8) when you hit it with your pact weapon. You also critically strike on 19's and 20's on a d20.

Boon of Karsus; Improved Eldritch Master: In the heat of combat, power lent by Karsus allows you to reduce the one minute timer of Eldritch Master to one bonus action, regaining all of your spell slots.

Scythe of Karsus; Haste: The Scythe is sentient and can cast Haste for you on command provided you spend a bonus action commanding it to do so. The scythe casts this for you and will also hold concentration on the spell. It can do this once per day recharging at dusk.

Armor of Hexes: If a target afflicted by your Hexblades curse hits you with an attack roll, you can use your reaction to roll a d6. On a 4 or higher, the attack misses you, regardless of the roll.

Boon of Spell Mastery: You can cast Hellish Rebuke at 3rd level without expending a spell slot.